Actuator or suspension

Abstract

An actuator whose total length can be reduced is provided. An actuator (2) includes: a casing (7); a hollow shaft (8) rotatably supported by the casing (7) via a bearing (9a, 9b), the hollow shaft (8) including a bottom portion (8b); a screw shaft (14) coupled to the bottom portion (8b) of the hollow shaft (8), the screw shaft (14) sharing a common center line with the hollow shaft (8); and a nut (15) threadedly connected to the screw shaft (14). The nut (15) is capable of moving in an axial direction of the screw shaft (14) to enter between the hollow shaft (8) and the screw shaft (14).

The invention claimed is: 
     
       1. An actuator comprising:
 a casing; 
 a hollow shaft rotatably supported by the casing via a bearing, the hollow shaft including a bottom portion; 
 a screw shaft coupled to the bottom portion of the hollow shaft, the screw shaft sharing a common center line with the hollow shaft; and 
 a nut threadedly connected to the screw shaft, wherein 
 the screw shaft is coupled to the hollow shaft so as to be incapable of rotating relative to the hollow shaft and incapable of moving in an axial direction relative to the hollow shaft, and 
 the nut is capable of moving in an axial direction of the screw shaft to enter between the hollow shaft and the screw shaft. 
 
     
     
       2. The actuator according to  claim 1 , wherein
 a projection is fixed to an outer surface of the casing, and 
 the nut is coupled to an anti-rotation member configured to prevent the rotation of the nut, the anti-rotation member including a groove formed to allow the projection to fit therein. 
 
     
     
       3. The actuator according to  claim 2 , wherein the anti-rotation member is provided with a stopper configured to come into contact with the projection and restrict the movement of the nut relative to the casing in the axial direction. 
     
     
       4. A suspension comprising the actuator according to  claim 3 . 
     
     
       5. A suspension comprising the actuator according to  claim 2 . 
     
     
       6. A suspension comprising the actuator according to  claim 1 . 
     
     
       7. The suspension according to  claim 6 , wherein
 the nut is coupled to an inner rod of a shock absorber, and 
 a hollow portion of the inner rod allows the screw shaft to enter. 
 
     
     
       8. The suspension according to  claim 7 , wherein the screw shaft is rotationally driven by a drive unit, and the nut is moved relative to the screw shaft in an axial direction to adjust the height of a vehicle. 
     
     
       9. The suspension according to  claim 7 , wherein the screw shaft is connected to a motor for producing a damping force. 
     
     
       10. The suspension according to  claim 6 , wherein the screw shaft is rotationally driven by a drive unit, and the nut is moved relative to the screw shaft in an axial direction to adjust the height of a vehicle. 
     
     
       11. The suspension according to  claim 6 , wherein the screw shaft is connected to a motor for producing a damping force. 
     
     
       12. A suspension comprising:
 a casing; 
 a screw shaft rotatably supported by the casing via a bearing; 
 a nut threadedly connected to the screw shaft; and 
 a shock absorber including an inner rod, wherein 
 the nut is coupled to the inner rod of the shock absorber, 
 the inner rod is coupled to the nut so as to be incapable of rotating relative to the nut and incapable of moving in an axial direction relative to the nut, and 
 a hollow portion of the inner rod allows the screw shaft to enter. 
 
     
     
       13. The suspension according to  claim 12 , wherein the screw shaft is rotationally driven by a drive unit, and the nut is moved relative to the screw shaft in an axial direction to adjust the height of a vehicle. 
     
     
       14. The suspension according to  claim 12 , wherein the screw shaft is connected to a motor for producing a damping force. 
     
     
       15. A suspension comprising:
 a casing; 
 a screw shaft rotatably supported by the casing via a bearing; 
 a nut threadedly connected to the screw shaft; 
 a projection fixed to an outer surface of the casing; and 
 an anti-rotation member coupled to the nut, including a groove formed to allow the projection to fit therein, to prevent the rotation of the nut, 
 wherein the anti-rotation member is coupled to the nut so as to be incapable of rotating relative to the nut and incapable of moving in an axial direction relative to the nut. 
 
     
     
       16. The suspension according to  claim 15 , wherein the screw shaft is rotationally driven by a drive unit, and the nut is moved relative to the screw shaft in an axial direction to adjust the height of a vehicle. 
     
     
       17. The suspension according to  claim 15 , wherein the screw shaft is connected to a motor for producing a damping force.